1. Field of the Invention
The present invention relates to internal combustion engines and, more particularly, to a carburetion system for compressed air assisted injection.
2. Prior Art
The present invention relates to fuel injection systems for internal combustion engines and, more specifically, to the control of a low pressure injection in an internal combustion engine. A particular field of application of the invention is a two-stroke internal combustion engine. The specific application described is to a small high speed two-stroke engine, such as utilized in handheld power equipment such as leaf blowers, string trimmers and hedge trimmers, also in wheeled vehicle applications such as mopeds, motorcycles and scooters, and in small outboard boat engines. The small two-stroke engine has many desirable characteristics, that lend themselves to the above applications, including: simplicity of construction, low cost of manufacturing, high power-to-weight rations, high speed operational capability and, in many parts of the world, ease of maintenance with simple facilities.
The prominent drawback of the simple two-stroke engine is the loss of a portion of the fresh unburned fuel charge from the cylinder during the scavenging process. This leads to poor fuel economy and, most importantly, high emission of unburned hydrocarbon, thus rendering the simple two-stroke engine incapable of compliance with increasingly stringent governmental pollution restrictions. This drawback can be relieved by separating the scavenging of the cylinder, with fresh air, from the charging of the cylinder, with fuel. This separation can be achieved by injecting the liquid fuel into the cylinder or more preferably by injecting the fuel charge by utilizing a pressurized air source, separate from the fresh air scavenge, to spray the fuel into the cylinder. In a preferred embodiment of the present invention, the displacement size of the engine is about 16 cc to about 100 cc, but could be larger or smaller. These sizes of engines are used for such things as string trimmers, chain saws, leaf blowers, and other hand held power tools. The engine could be also be used on a tool such as a lawn mower, snow blower or motor boat outboard engine.
In accordance with one embodiment of the present invention, an internal combustion engine is provided having a crankcase, a cylinder connected to the crankcase, a compressed air assisted fuel injection system connected between the crankcase and the cylinder, and a reciprocating piston head located in the cylinder. The improvement comprises a fuel delivery system having two carburetors that switch delivery of fuel to two different locations based upon the speed of the engine. The system uses an accumulator with piston ported reflected compression wave delivery of scavenged compressed air to deliver fuel at a wide open throttle position.
In accordance with another embodiment of the present invention, a carburetor system for use with an internal combustion engine is provided comprising a frame forming two air conduits; a fuel metering device connected to the frame for delivering fuel to the two air conduits; and a fuel delivery varying system for varying amounts of fuel delivered from the fuel metering device to the two air conduits when speed of the engine or load on the engine changes. The fuel delivery varying system is adapted to increase fuel delivery to a first one of the air channels with a substantially simultaneous decrease in fuel delivery to a second one of the air channels.
In accordance with one method of the present invention, a method of delivering fuel in a carburetor to an internal combustion engine is provided comprising steps of: delivering fuel to a first air channel of the carburetor; delivering fuel to a second air channel of the carburetor; and decreasing fuel delivery to the first air channel when fuel delivery is increased to the second air channel; wherein fuel is delivered through the first and second air channels to two respective spaced locations for delivery to a same cylinder of the engine, and wherein a flow rate and piston cycle of fuel delivery to a first one of the spaced locations through the first air channel is decreased as a flow rate per piston cycle of fuel delivery to a second one of the spaced locations through the second air channel is increased.
In accordance with another method of the present invention, a method of delivering fuel in a carburetor to a two-stroke internal combustion engine is provided comprising steps of: delivering fuel to a fuel and air delivery channel in the carburetor; and varying an amount of fuel being delivered to the fuel and air delivery. channel based, at least partially, upon suction generated by air being pulled through a main air channel of the carburetor into a crankcase of the engine, wherein substantially all the fuel in the fuel and air delivery channel is introduced into a combustion chamber of the engine without passing through the crankcase.
In accordance with another embodiment of the present invention, an internal combustion engine is provided having a crankcase, a cylinder connected to the crankcase, a compressed air assisted fuel injection system connected between the crankcase and the cylinder, and a reciprocating piston head located in the cylinder. The improvement comprises a fuel delivery system having two carburetors with a throttle shaft extending into the two carburetor sections.
In accordance with another embodiment of the present invention, a carburetor system for use with an internal combustion engine is provided comprising a first carburetor section; a second carburetor section; and a common throttle shaft assembly extending through both the first and second carburetor sections. The shaft assembly comprises a throttle plate located in a main air passageway of the first carburetor section and a throttle shaft having the throttle plate connected thereto. The throttle shaft extends into a channel in the second carburetor section and is rotatable to increase and decrease a flow path through the channel as the shaft is rotated.
In accordance with another method of the present invention, a method of controlling delivery of fuel/air mixtures in a carburetor system for an internal combustion engine is provided comprising steps of providing the carburetor system with two carburetor sections for creating two different fuel/air mixtures and a common control shaft assembly which extends through two separate conduits in the respective two carburetor sections; and rotating the common control shaft assembly to open or restrict pathways through the two conduits, wherein a first one of the conduits is smaller than a second one of the conduits, and wherein the control shaft comprises a plate attached to the control shaft in the first conduit and a hole through the control shaft at the second conduit, wherein the hole can be aligned with and misaligned with the second conduit when the control shaft is rotated to open or restrict the pathway through the hole and the second conduit.
In accordance with another embodiment of the present invention, an internal combustion engine is provided having a crankcase, a cylinder connected to the crankcase, a compressed air assisted fuel injection system connected between the crankcase and the cylinder, and a reciprocating piston head located in the cylinder. The improvement comprises a fuel delivery system having two carburetor sections with a throttle shaft assembly and a choke shaft assembly operably connected to two air flow channels of the two carburetor sections.